Thailand's capital, Bangkok, is scrambling to fend off flood waters bearing down on the city. Unusually heavy rains have caused the worst flooding in decades across Southeast Asia, killing some 500 people, destroying crops and flooding homes and factories.

The Thai capital Thursday reinforced dikes holding off floodwaters that have ravaged central and northern parts of the country.

Bangkok is preparing for high water expected this weekend as run-off from those floods reach the city just as seas in the Gulf of Thailand reach high tide.

Sean Boonpracong, international spokesman for Bangkok's flood relief center, acknowledges that flooding in the capital is a possibility but says authorities are doing all they can to prevent it.

"I think there are a small risk of flooding in the outer area," said Boonpracong. "But, for now I believe it is manageable. There has been a new operation to relieve the water."

Boonpracong says authorities are dredging canals in Bangkok’s Chao Phraya and other rivers so more water can reach the sea faster.

Authorities were forced to release water from a few dams at once, leading rivers to burst their banks.

Smith Dhamasarojana is former director-general of Thailand's Meteorological Department. He is now chairman of the National Disaster Warning Council Foundation, a non-profit group that tries to urge Thailand and its neighbors to better prepare for disasters. He says authorities in Thailand did not release enough water from the dams earlier in the year because they were afraid of a water shortage in the dry season.

"They mis-underestimate the amount of rainfall and they mis-underestimate how to manage the water," he said. "They cannot direct the route of water to the sea fast enough.”

Thailand is not the only country affected by the unexpected rains. Hundreds have been killed in flooding in Cambodia, Laos and Vietnam.

Heavy crop losses are also expected in the world’s two biggest rice-exporting countries - Thailand and Vietnam.

Bhupinder Tomar is head of operations in Hanoi for the International Federation of the Red Cross.

“The biggest damage has been, as you can imagine, this being the rice production bowl of Vietnam, the biggest damage has been to economic livelihood and the losses to crops, both standing and planted, has been tremendous," said Tomar. "In fact about 7,000 hectares of rice crop has been lost completely, and total hectares lost has been about 30,000, which means about, roughly 60,000 families have been affected by these losses so far.”

Southeast Asia has had several tropical storms this monsoon season, which some analysts say may be due to rising global temperatures.

Further rain is expected in the southern part of Thailand in the coming days.

The impending waters have led to some panic buying in Bangkok grocery stores as residents stock up on bottled water and food.

Spokesman Boonpracong says despite the clearing of some market shelves there will not be any food shortages.

He says authorities have prepared emergency food and water as well as 70-some evacuation centers in case the city’s dikes are breached.